The structure of ribonuclease-T1 is known from xray crystallography at high resolution with bound ligand, 2'GMP. The ligand binding site is situated opposite to the single Trp residue at position 59. Ligand binding is known to induce changes in the fluorescence lifetime of Trp-59 which may be mediated mechanically through the protein matrix rather than direct through-space interaction of the ligand and the Trp fluorophore. I have measured the fluorescence intensity decay of wildtype ribonuclease-T1 and several single-site mutants under various conditions of ligand and quencher concentration using the TCSPC technique. The results were interpreted, with supporting molecular dynamics simulation, as allosteric interactions not associated with protein or subunit conformational change upon ligand binding. Further measurements of the anisotropy are underway.